Journal of Himalayan Earth Sciences 46(2) (2013) 113-119 Estimation of groundwater balance for the Pabbi region, Khyber Pakhtunkhwa Tabinda Masud1, Amjad Ali1, Hazrat Hussain2, Khan Shahzada1, Bashir Alam1, Noreema Masud3 and Muhammad Rizwan1 1Faculty member, Department of Civil Engineering, UET, Peshawar 2Principal, Government Advance Technical Training Centre, Hayatabad, Peshawar 3Faculty member, Department of Civil Engineering, CECOS University of IT & Emerging Sciences, Peshawar Abstract This paper presents the study carried out to estimate groundwater balance for the Pabbi Region, Khyber Pakhtunkhwa. Due to heavy rainfall, excessive irrigation and seepage from irrigation canals, the adjacent areas of Kabul River in the study area have suffered from water logging for a long time. It has been calculated that the recharge to groundwater storage due to seepage from canals and their distributaries flowing in the Pabbi Region is 26 mm/year. According to the data collected from Pakistan Meteorological Department, Peshawar, mean annual rainfall of Pabbi Region is 262.77 mm/year and recharge due to rainfall is calculated as 60.63 mm/year. Discharge through tube wells and hand pumps in the area are estimated as 35 mm/year and 14 mm/year respectively. It has been concluded that the average increase in groundwater level in the study area is 37.63 mm/year. Keywords: Pabbi; Pakistan; Groundwater balance; Rainfall; Discharge and water logging. 1. Introduction of Kabul River in Khyber Pakhtunkhwa was about 21.34-24.39 m (70-80 ft) below the ground level Total area of Pabbi region is 427.5 km2. Its at the time of establishing irrigation system. By geographical coordinates are 34°00′38″ N and 1925 water table came up to 12.20 m (40 ft) and 71°47′56″ E. It is bounded by Kabul River in the in 1940 up to 7.62 m (25 ft) below ground level. north, Bara River in the west, Cherat Mountains in In 1960 it reached 3.05-3.66 m (10-12 ft) and the south and Nowshera City in the east. The finally in 1970 it reached as close as 0.61-0.91 m study area (Fig. 1) has ten union councils: Pabbi, (2-3 ft) of the ground level and even touched the Khashor Garhi, Dak Behsaal, Jallozai, Dak Ismail ground surface in rainy season. A decrease by Khel, Spin Khak, Shah Kot, Chowk Mumraiz, more than 50% in the yield has also been recorded Taru and Dagi. in this connection. It was not before 1980 that the problem was diagnosed and remedies started. Recharge to the groundwater storage in the Water and Power Development Authority area under study mainly takes place due to (WAPDA) used a number of techniques for precipitation and seepage from canals. According reducing the level of water table. These to Irrigation Department, Peshawar, depth of water techniques included construction of surface table from the ground surface of study area varies drains, installation of tube wells and construction from 3.05 m (10 ft) in Pabbi to 18.29 m (60 ft) in of subsurface tile drains (Javed and Nasim, 2005). Jaroba. In order to fulfill the desired demand of water The canals and distributaries flowing in the for increasing population (annual growth rate of study region (Fig. 2) are: Warsak Gravity Canal, 2.9%) of the study area, some more tube wells Warsak Lift Canal, Kabul River Canal and Hazar were installed by Irrigation Department Peshawar, Khani Canal. The level of water table in Mardan, Public Health Engineering Department Pabbi and Nowshera, Pabbi, Swabi and areas in the vicinity Tehsil Municipal Administration Pabbi with the 113 passage of time. Residents of the study area have where, S = seepage loss (ft3/sec per km of canal) installed hand pumps in their homes to discharge and Q = channel discharge (ft3/sec). groundwater for their domestic use. It is an exigency of the time to evaluate the present Infiltration due to precipitation is found by taking situation of groundwater balance in the area under a difference of precipitation and surface run off. study and to take the remedial measures in case of SCS Curve Number Method (Das, 2000) is used the risk of water logging. to find surface run off and is given as: 2. Methodology = − 2 + Q [P 0.2S M ] /[P 0.8S M ] This study is carried out to estimate the current situation of groundwater balance for the where, Q = surface run off (mm), P = average Pabbi region for which recharge to and the rainfall (mm), and S M = soil moisture capacity. discharge from groundwater has been found. 100 = ∗ − SM 254 1 2.1. Recharge to the groundwater CN where, CN = Curve Number Seepage from canals, infiltration due to precipitation, water applied for irrigation and The curve number for a particular soil water stored in depression storages play an depends upon the characteristic of basin and soil important role in increasing groundwater level. In moisture condition at the time of occurrence of this study, the first two factors, being mainly rainfall. responsible for recharging groundwater of the project area are considered. The weighted curve number is the average curve number representing different land use Nazir formula (Ahmad et al., 2007) is used to conditions of the area which are classified by measure seepage from canals and is given as: hydrological soil groups (Table 1). 0.04Q 0.68 S = 1.61 Fig. 1. Site map of the study area. (Source: Google Earth. Not to scale) 114 Fig. 2. Map of canals in the study area. (Source: Water and Power Development Authority (WAPDA). Not to scale) Table 1. Hydrological soil groups S. No. Soil Group Type of Soil Run off Potential 1 A sand, loamy sand or sandy loam Low 2 B silt loam or loam Moderate 3 C sandy clay loam High 4 D clay loam, silty clay loam, sandy Very High clay, silty clay or clay 2.2. Discharge from groundwater five houses of each union council are visited. Number of people in these houses is counted and Tube wells, dug wells, hand pumps, sub- discharge through hand pumps is found by surface drains and evapotranspiration are measuring the period of time required to fill a responsible for decreasing groundwater level. The container of known volume. factors considered in this study are tube wells and hand pumps. 3. Results and discussion Data of tube wells discharge is collected from 3.1. Recharge to groundwater Tehsil Municipal Administration Pabbi, Public Health Engineering Department Pabbi and Seepage loss through canals and part of Irrigation Department Peshawar. To calculate the precipitation, infiltrated into the soil, play an amount of water withdrawn through hand pumps, important role in increasing groundwater level of a survey of all union councils is conducted i.e. the Pabbi region. 115 3.1.1 . Seepage from canals 0.36 m3/s by Nazir formula (Tables 2 and 3). There is no lined section of Kabul River Canal Warsak Lift Canal and the distributary of flowing in the study area; however, seepage loss Kabul River Canal i.e. Hazar Khani Canal, passing through the lined sections of Warsak Gravity through the study area, are lined with cement Canal, being very small, is considered as concrete. Since seepage losses through lined canals negligible. are very small, therefore, recharge due to seepage Dividing the seepage loss (0.36 m3/s) by total through these canals has been neglected. 2 area (427.50 km ), increase in groundwater Seepage loss through the other two canals i.e. recharge is found as 8.42 * 10-10 m/sec. Thus, the Warsak Gravity Canal and Kabul River Canal, groundwater level of the Pabbi region is increased passing through the study area, has been found as by 26 mm per year. Table 2. Measurement of seepage loss through Warsak gravity canal RD-RD Length, *E/L Discharge, Seepage Loss per km of length Seepage Loss = 0.68 L Q 0.04Q 3 SL : S = (ft /sec / km) 3 (km) (ft3/sec) 1.61 (m /s) 145+900–147+700 0.55 E 50.52 0.36 0.006 147+700–150+400 0.82 E 47.69 0.34 0.008 150+400–152+600 0.67 E 38.78 0.30 0.006 152+600–155+600 0.92 E 36.00 0.28 0.007 155+600–159+300 1.13 E 36.00 0.28 0.009 159+300–161+400 0.64 E 27.47 0.24 0.004 161+400–162+900 0.46 E 25.01 0.22 0.003 162+900–168+900 1.83 E 20.86 0.20 0.010 168+900–169+900 0.31 E 16.87 0.17 0.001 169+900–170+900 0.31 L --- 0 0 170+900–171+900 0.31 E 14.52 0.15 0.001 171+900–174+900 0.92 L --- 0 0 174+900–175+900 0.31 L --- 0 0 175+900–178+900 0.92 L --- 0 0 178+900–183+400 1.37 E 11.11 0.13 0.005 183+400–186+300 0.88 L --- 0 0 186+300–186+900 0.18 E 10.00 0.12 0.001 Total seepage = 0.061 * E = Earthen (unlined) section of a canal L = Lined section of a canal Table 3. Measurement of seepage loss through Kabul River Canal. Length, *E/L Discharge, Seepage loss per canal km Seepage Loss = 3 0.68 RD-RD L Q (ft /sec) 0.04Q 3 SL : S = (ft /sec / km) 3 (km) 1.61 (m /s) 43+200–49+204 1.83 E 281 1.15 0.06 49+204–56+194 2.13 E 281 1.15 0.07 56+194–61+181 1.52 E 281 1.15 0.05 61+181–66+168 1.52 E 281 1.15 0.05 66+168–71+155 1.52 E 281 1.15 0.05 71+155–7 2+155 0.31 E 281 1.15 0.01 Total seepage = 0.30 * E = Earthen (unlined) section of a canal L = Lined section of a canal 116 3.1.2.